1. Technical Field
The present invention relates to a portable data storage apparatus, more particularly, a memory card that contains a non-volatile memory.
2. Discussion of Related Art
A smartcard—a type of memory card—is a card embedded with a memory in which data can be stored and retrieved. The smartcard receives its power from external sources like a card reader. Typically the memory inside this kind of memory card is a non-volatile memory such as EPROM, EEPROM or FLASH memory.
When connected with external sources like an electronic device, a memory card operates with a power supplied from the electronic device. When the power (hereinafter, referred to as an external supply voltage) supplied from the electronic device deviates from an operating voltage range of a non-volatile memory in the memory card, the non-volatile memory may not operate properly. For example, if the external supply voltage is lowered while writing/reading data in/from the non-volatile memory, erroneous data can be written/read in/from the non-volatile memory.
With conventional technology, lowering of an operating voltage of the non-volatile memory is limited due to a characteristic of the non-volatile memory that needs higher voltages than the external supply voltage. Furthermore, although an electronic device may operate with a low voltage (e.g. below 1.8V), it may be difficult to use a memory card having a non-volatile memory because non-volatile memories exhibit poor operating characteristics at low voltage. In other words, if a memory card having a non-volatile memory is applied to the low-voltage electronic device, the memory card may not operate reliably.
Therefore, a need exist for a power management system which can secure a stable operation of the non-volatile memory even when a memory card is supplied with an external supply voltage deviating from an operating voltage range of a non-volatile memory in the memory card.